Many pearlescent or nacreous pigments are based on the use of a laminar substrate such as mica which have been coated with a metal oxide layer. As a result of reflection and refraction of light, these pigments exhibit pearl-like luster and depending on the thickness of the metal oxide layer, they can also exhibit interference color effects. The pearlescent pigments encountered on a commercial basis are most often either titanium dioxide-coated mica or iron oxide-coated mica pearlescent pigments. Both types are well known in the art.
The overcoating of the titanium dioxide-coated or iron oxide-coated mica pearlescent pigment is also well known in the art. See, for example, U.S. Pat. Nos. 3,087,828, 3,087,829, 3,711,308, 3,874,890, 4,146,403, 4,886,100, and 5,137,575.
Copper chromite, also known as Pigment Black 28, is a black material. When it is coated in a sufficient quantity on a laminar or platy substrate such as mica, the coating is opaque. In contrast, pearlescent pigments are based on the fact that there is reflection at the surface of the coating and also a transmission through the coating to the next interface, and reflection at that next interface.
It has now been surprisingly discovered that if copper chromite is coated onto a metal oxide-coated, e.g. a titanium dioxide- or iron oxide-coated mica pearlescent pigment, there is color advancement of the interference color and an increase in the opacity of the pigment. It has also been found that if the layer is thick enough, the color progresses to the next shade and 100% opacity can be achieved at lower pigment loads.
It has also been found that copper chromite can be coated onto a platy substrate, e.g., mica, kaolin, etc., and then coated with a metal oxide layer which produces colored black pigments. The initial layer of copper chromite can be of sufficient quantity to be opaque (about 45% CuCr2O4 when the substrate is mica) or semitransparent.
It is therefore the object of this invention to provide new black pearlescent pigments. This and other objects of the invention will become apparent to those of ordinary skill in this art from the following detailed description.
This invention relates to black colored metal oxide pearlescent pigments and more particularly to iron oxide-coated mica or titanium dioxide-coated mica pearlescent pigments which have a coating of copper chromite thereon. The coating of copper chromite can either be on the surface of the metal oxide or between the interface of the metal oxide and the mica or other laminar or platy substrate.
In accordance with the present invention, a black colored pearlescent pigment is obtained by coating a metal oxide-coated mica pearlescent pigment with copper chromite or coating the mica with copper chromite and then forming the metal oxide layer on top thereof.
Both titanium dioxide-coated mica pearlescent pigments and iron oxide-coated mica pearlescent pigments are well known in the art. They are generally formed by depositing a hydrous titanium or iron compound on the mica substrate followed by hydrolysis and calcining to produce the TiO2- or Fe2O3-mica pigment. Any of the known metal oxide coated mica pigments can be used in the present invention.
The copper chromite can be deposited on the pearlescent pigment by any convenient procedure. It is preferred to first precipitate chromium onto the surface of the pigment, for example, by contacting the pigment with a chromium chloride solution and maintaining an appropriate pH with a suitable base such as sodium hydroxide, potassium hydroxide or the like. This is followed by the contacting of the pigment with a copper chloride solution and maintaining an appropriate pH with a suitable base such as sodium hydroxide, etc. There is no preference as to which metal is deposited first. The invention is not limited to the use of copper chloride or the above procedure and other appropriate copper materials such as copper nitrate and/or procedures can be used if desired. For instance, after contact with a copper solution at an appropriate pH, chromic acid can be added and the pH adjusted to cause the formation of the copper chromite. Finally, the product can be calcined for about 20 minutes at about 550 to 900xc2x0 C.
The amount of copper chromite can be varied in order to obtain the desired color and/or opacity. For example, the amount of copper chromite can vary from about 1 to 50%, preferably about 5 to 35%, based on the weight of the pearlescent pigment. As the amount of copper chromite is increased, there is a progression in the interference color and an increase in the opacity of the pearlescent pigment.
The products of the present invention can be used in any application where pearlescent pigments have been used heretofore. Non-limiting examples include various cosmetic formulations, printing inks, colorants for plastic resins, coatings and automotive paints.
Products of this invention have an unlimited use in all types of automotive and industrial paint applications, especially in the organic color coating and inks field where deep color intensity is required. For example, these pigments can be used in mass tone or as styling agents to spray paint all types of automotive and non-automotive vehicles. Similarly, they can be used on all clay/formica/wood/glass/metal/ enamel/ceramic and non-porous or porous surfaces. The pigments can be used in powder coating compositions. They can be incorporated into plastic articles geared for the toy industry or the home. These pigments can be impregnated into fibers to impart new and esthetic coloring to clothes and carpeting. They can be used to improve the look of shoes, rubber and vinyl/marble flooring, vinyl siding, and all other vinyl products. In addition, these colors can be used in all types of modeling hobbies.
The above-mentioned compositions in which the compositions of this invention are useful are well known to those of ordinary skill in the art. Examples include printing inks, nail enamels, lacquers, thermoplastic and thermosetting materials, natural resins and synthetic resins. Some non-limiting examples include polystyrene and its mixed polymers, polyolefins, in particular, polyethylene and polypropylene, polyacrylic compounds, polyvinyl compounds, for example polyvinyl chloride and polyvinyl acetate, polyesters and rubber, and also filaments made of viscose and cellulose ethers, cellulose esters, polyamides, polyurethanes, polyesters, for example polyglycol terephthalates, and polyacrylonitrile.
For a well-rounded introduction to a variety of pigment applications, see Temple C. Patton, editor, The Pigment Handbook, volume II, Applications and Markets, John Wiley and Sons, New York (1973). In addition, see for example, with regard to ink: R. H. Leach, editor, The Printing Ink Manual, Fourth Edition, Van Nostrand Reinhold (International) Co. Ltd., London (1988), particularly pages 282-591; with regard to paints: C. H. Hare, Protective Coatings, Technology Publishing Co., Pittsburgh (1994), particularly pages 63-288. The foregoing references are hereby incorporated by reference herein for their teachings of ink, paint and plastic compositions, formulations and vehicles in which the compositions of this invention may be used including amounts of colorants. For example, the pigment may be used at a level of 10 to 15% in an offset lithographic ink, with the remainder being a vehicle containing gelled and ungelled hydrocarbon resins, alkyd resins, wax compounds and aliphatic solvent. The pigment may also be used, for example, at a level of 1 to 10% in an automotive paint formulation along with other pigments which may include titanium dioxide, acrylic lattices, coalescing agents, water or solvents. The pigment may also be used, for example, at a level of 20 to 30% in a plastic color concentrate in polyethylene.
In the cosmetic field, these pigments can be used in the eye area and in all external and rinse-off applications. They are restricted only for the lip area. Thus, they can be used in hair sprays, face powder, leg-makeup, insect repellent lotion, mascara cake/cream, nail enamel, nail enamel remover, perfume lotion, and shampoos of all types (gel or liquid). In addition, they can be used in shaving cream (concentrate for aerosol, brushless, lathering), skin glosser stick, skin makeup, hair groom, eye shadow (liquid, pomade, powder, stick, pressed or cream), eye liner, cologne stick, cologne, cologne emollient, bubble bath, body lotion (moisturizing, cleansing, analgesic, astringent), after shave lotion, after bath milk and sunscreen lotion.
In order to further illustrate the invention, various examples are set forth below. In these examples, as well as throughout this specification and claims, all parts and percentages are by weight and all temperatures are in degrees Centigrade, unless otherwise indicated.